[Zope] set / change modification time of an object directly

hi all, every object inside Zope (i.e. of the ZODB) has got its own modification time. If you have access to an object inside a product, for example via "my_obj = self.restrictedTraverse(obj_path)", you can get a human readable version of that modification time with "my_obj.bobobase_modification_time()", calling that certain method everyone knows. is it possible to get access to the modification time attribute of the object directly ? what about "my_obj._p_mtime" ? how can one set / update / change ? thanks, Andreas Hoelzl